Rapid, simple, and cost-effective treatments to achieve long-term hydrophilic PDMS surfaces

This paper describes rapid, simple, and cost-effective treatments for producing biocompatible and long-term hydrophilic polydimethylsiloxane (PDMS) surfaces identified in an experimental study investigating 39 treatments in all. The wetting of the surfaces was monitored during six months. Changes in surface morphology and chemical composition were also analyzed. Some of the treatments are presented here for the first time, while for earlier presented treatments the selection of investigated 2 parameters was wider and the observation period for the surface wetting longer. The PDMS surfaces were modified by surface activation, physisorption, and synthesis of both “grafting to” and “grafting from” polymer brushes. In surface activation, the PDMS sample was exposed to oxygen plasma, with several combinations of exposure time and RF power. In the physisorption and synthesis of polymer brushes, three commercially available and biocompatible chemicals were used: 2-hydroxyethyl methacrylate (HEMA), polyethylene glycol (PEG), and polyvinylpyrrolidone (PVP). Thirty-three of the 39 treatments rendered the PDMS hydrophilic, and in 12 cases the hydrophilicity lasted at least six months. Seven of these long-term hydrophilic coatings supported a contact angle of 30° or less. Three of the long-lasting hydrophilic coatings required only minutes to prepare.